Couple John and Marci Newman have been married for 18 years and counting. In today’s day and age, that’s become a bit of a rarity. A viral tweet posted by their daughter, however, reveals something about why they’re still going strong.

In April of 2017, the couple’s 17-year-old daughter, Mackenna, snapped a picture of her father sitting at a desk outside his and his wife’s bedroom door. There’s a lovely story behind this simple gesture, and tens of thousands of netizens appreciated it.

At first, the image—which garnered a viral response on Twitter—looks a bit odd. John is sitting just outside their bedroom with the door open just a crack.

He is just passing the time for some reason that requires an explanation

My mom has to stay in her room in isolation for her cancer radiation so my dad set up a desk at her door to keep her company and I’m crying pic.twitter.com/rucH9HfDvk

Mackenna’s comment tells the rest of the story, and the sentimental message went viral right away. Mackenna tweeted:

My mom has to stay in her room in isolation for her cancer radiation so my dad set up a desk at her door to keep her company and I’m crying

The previous year, Marci had been diagnosed with thyroid cancer.

A few weeks before the photo was snapped, she underwent what’s known as radioactive iodine treatment, which is a form of radiation therapy used to target isolated cancer cells in the body.

Since the radiation used in the pills is much higher than in other forms of radiation treatment, the recipient runs the risk of exposing others to radiation he or she gives off in the days following the treatment.

As a result, while the family was optimistic that the treatment would prove successful, it was a harrowing process for all involved

To prevent Marci from exposing John and Mackenna to radiation, she had to remain isolated in her room for just under a week, all alone—though her husband saw to it she was not lonely.

John obviously would not enter the room and risk radiation exposure.

“The first day,” Mackenna explained, “he sat outside in the backyard.” From there, he had talked to Marci using the window as their barrier. That proved unpractical however, so he set up his station outside the room and had been there since then.

Mackenna’s tweet of her dad garnered over 70,000 shares and well over 900 responses since then.

Some expressed support, and others shared similar experiences, such as this one:

My mom has to stay in her room in isolation for her cancer radiation so my dad set up a desk at her door to keep her company and I’m crying pic.twitter.com/rucH9HfDvk

Mackenna revealed that her dad attended her mom’s every doctor’s visit—no matter how small—even blood tests. Such gestures are full of meaning, and that love is perhaps as good as (if not better than) any treatment or medicine one could ask for!